Nonextremal extreme single coronoid

Fig. 6.6. One isomer each of the smallest nonextremal extreme single coronoids. The inscribed numerals indicate the number of last added hexagon during the modified spiral walk.

Fig. 5.7. Examples of nonextremal extreme single coronoids which are not naphthalenic.

Formula. In accord with the above description every nonextremal extreme single coronoid (X) corresponds to an extremal single coronoid, A( ), for which A(hr-l) -i A(h) is accompanied by An = 2. The formulas of these special A coronoids are obtained from eqn. (57), but starting the running index from h = 1 i.e. h = 1, 2, 3, 4,...These A coronoids are associated with the... 

Property 6,4- A nonextremal extreme single coronoid X has never a fjord except for the inner fjords of its naphthalene hole if the system is naphthalenic. 

In other words, any extremal single coronoid (A) can be circumscribed without limitation. However, there also exist nonextremal single coronoids which are reproducible and therefore can be circumcscribed without limitation. Kekulene is an obvious example. 

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